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PHOENIX -- We are living longer and longer. More than 80,000 people in the U.S. today are older than 100.

If you want to be healthy and active those last 20 or 30 years, you need to start planning now.

Scott Pasmore sat down with Dr. Walter Gaman, co-author of a book called "Stay Young: 10 Proven Steps to Ultimate Health," to talk about the mechanics of aging -- how and why it happens -- and some tests you might want to consider having, including a hormone assessment, micronutrient testing, a bone scan, a Vo2Max stress test and a carotid doppler.